Many substances and materials have been used to form containers for natural and artificial plants and flowers, referred to generally here as floral containers. Glass, clay, pottery, wood, polymers of many kinds, etc., for example, have been formed and used as floral containers.
It is also known to make shaped objects of an infinite variety of sizes and shapes using foamed polymers. Christmas tree ornaments, animal and fanciful figurines, utilitarian shapes, packaging, etc., for example have been made of polyurethane and other foamed plastics.
The technology of polyurethane foams is reasonable well developed. See, for example, the comprehensive discussion in Harper, HANDBOOK OF PLASTICS AND ELASTOMERS McGraw-Hill Book Company, 1975 and the current and past editions of the MODERN PLASTICS ENCYCLOPEDIA, as well as various treatises on urethane, polyurethane, plastic and elastomeric foams, isocyanates, etc.
One of the technologies reasonably well developed is that of forming polyurethane foams, either rigid or flexible, inside various containers to provide for strength, rigidity, continued buoyancy, or to provide other characteristics. For example, it is common in the boat industry to fill certain voids in the boat with closed-cell polyurethane foam. This renders that portion of the boat to be permanently buoyant and, if in sufficient volume compared with the displacement volume of the vessel, may render the entire vessel essentially unsinkable even though capsized.
Rigid polyurethane foams are used in various molded configurations to provide insulation as well as strength. For example, it is a fairly wide spread practice to use rigid polyurethane foam, typically foamed in place, between to shells of a refrigeration container, either a portable container or industrial container. The literature is replete with descriptions of various applications of rigid polyurethane foam technology in refrigeration and structural applications.
Typical rigid polyurethane products have a density of about 1.5 to 70 pounds per cubic foot with foams having a density generally in the 1.5 to 10 lb/ft.sup.3 range. Polyurethane foams tend to be self extinguishing and have low water absorption. Closed-cell polyurethane foams, i.e. foams in which each discreet cell is isolated from each other discreet cell, with no communication there between, are excellent insulators and provide buoyancy as well as great strength. In addition, closed-cell polyurethane can be used as a container, since the cells do not communicate one with another.
Polyurethanes generally and polyurethane foams of interest here are formed by the reaction of an isocyanate or polyisocyanate with a polyol, e.g. a diol or triol. The reaction is generally spontaneous and exothermic at normal room temperatures. In many structural and other applications, the reaction is caused to occur in situ, by mixing the isocyanate and polyol, along with suitable surfactants, catalysts, and buoying agents, and injecting the mixture, essentially instantaneously upon being mixed into the cavity to be filled. As the reaction proceeds, the foam forms and grows to fill the cavity. Various nozzles, pumps, mixing chambers, mixing heads and other equipment are available for mixing the components, i.e. the polyol and isocyanate, along with additives, for particular purposes.
In common formulations, the additives are added to one or the other of the components so that one has two constituents or two mixtures which, when mixed, react to form the desired polyurethane. For example, surfactants, which are usually silicone based surfactants for stabilizing the foam, controlling cell size and structure, and catalysts, to effect the time of cure, are mixed in one or the other of the materials, e.g. in the polyol or in the isocyanate. Blowing agents, or desired, may be dissolved in the `A` constituency mixture or in the `B` constituency mixture so that when the `A` and `B` mixtures are themselves mixed the buoying agent is activated thermally or chemically or otherwise and produces a gas which causes the polymer to expand and form a foam of the desired type. In some reactions, water, or another hydroxyl containing chemical, is added which results in the self-generation of carbon dioxide as a buoying agent. In many applications, however, it is desirable to dissolve a particular blowing agent in one of the other of the mixtures. For example, the FREON.TM. series of fluorocarbons and chlorofluorocarbons include a number of constituents which are excellent blowing agents which are soluble in either component `A` or component `B`, or both, and which, when heated, vaporize to form the desired foam composition. In rigid foams, of the type under consideration, fluorocarbons are usually the primary blowing agent with carbon dioxide being used occasionally as supplemental blowing agent.
The material of principal interest in respect to this invention is sometimes referred to as rigid, low density urethane foam, having a density of from about 1.5 to about 2.5 pounds per cubic foot. Density per se is not critical in this invention, however, and higher densities can as conveniently be used. This lower density foam is the type of urethane foam which is commonly used for thermal insulation in household refrigerators, freezers, picnic coolers, and other related products where low thermal conductivity is important. These foams have low thermal conductivity because of the high-molecular-weight flurorcarbon gas entrapped within the closed-cell structure of the foam. These foams can be used as containers, when in the suitable configuration, because of the closed-cell structure of the foam.
Among the isocyanates which are used in the manufacture of polyurethanes are tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and other polyisocyanates. Polyols used in the formation of polyurethane foams and other structures include glycerin, trimethylolpropane, 1,2,6-hexanetriol, alphamethylglycoside, pentaerythritol, sorbitol and sucrose. Rigid urethane foam formulations usually contain a polymeric isocyanate of the MDI type, e.g. 4,4'-diphenylmethane diisocyanate, and a non reactive blowing agent such as a fluorocarbon. Polyether polyols used in rigid urethane foams are generally more branched lowermolecular-weight types. Flame retardants may also be added but are not critical in the present application. Tertiary amines such as tetramethylguanidine, N,N,N prime, N prime-tetramethylbutanediamine, and dimethylaminoethanol are used in most rigid urethane foam formulations.
The machinery for preparing the foam formulation consists of principally of two or more metering pumps which feed the reactants to a continuous mixer at controlled rates and in desired proportions. The mixed output proceeds to the forming device in which the foam rises and cures.
The proceeding background on rigid polyurethanes foams is given to aide the reader in understanding the background of the invention, but it is not necessary that the reader understand the chemistry of this polymer system in order to take advantage of the present invention. Indeed, the present inventor is not a chemist and has arranged to provide this background only in the interest of clarity and completeness.
In the gift and floral industries, there is a continuing need for new and unique approaches to containing floral arrangements, including flowers, cut and growing, and plants generally, as well as other decorative items.
Both ornamental and utilitarian articles comprising ambient dimensionally stable polymer film, decorated or undecorated, plain or bearing printed or other indicia, may be manufactured according to the process of this invention.
It is anticipated that the present invention will have application in wide fields of commerce and industry. For example, it is contemplated that signs and displays generally which include lettering, etc., structural elements in which the stressed-skin and foam combination coact synergistically to give added strength, ornamental and utilitarian objects of all sizes and shapes can be made using the present invention. While the best mode and present advantages of the invention involve film containers in the form of balloons, i.e. a small-entry, large volume container, the invention is applicable to any shape of film container and to containers in which only part of the wall is in the form of a film. Reference is frequently made to balloons, merely as exemplary, to containers of these types.